In the field of toners for development of electrostatic latent images, with the progress of electrophotographic systems, it has been demanded to develop toners adaptable for high image quality and high copying speed.
In view of the high image quality and high copying speed, the toners are required to have various excellent properties. To meet these requirements for the toners, as a method of optionally controlling a particle size and surface properties of the toners, there has been proposed a process for producing a toner by an aggregating and unifying method (emulsification/aggregation method or aggregation/fusion method) in which a colorant, resin particles, etc., are aggregated by salting-out or the like method and fused together to obtain a single toner particle.
For example, Patent Document 1 discloses a process for producing a toner which includes a step of emulsifying a resin binder containing a polyester in an aqueous medium and a step of adding a water-soluble nitrogen-containing compound having a molecular weight of 350 or less to an emulsion of the resin binder obtained in the previous step to aggregate the emulsified particles, for the purpose of obtaining a toner having a narrow particle size distribution.
Patent Document 2 discloses a process for producing a toner which includes a step of fusing resin particles and colorant particles in the presence of a polymeric aggregating agent in an aqueous medium, for the purpose of obtaining a toner capable of stably forming images having a high image quality.
Patent Document 3 discloses a process for producing a developer which includes a step of adding a cationic organic coagulant having an average molecular weight of from 1,000 to 100,000 to a dispersion of fine particles as a mixture containing a resin binder and a colorant to aggregate the fine particles in the mixture and thereby form aggregated particles, for the purpose of obtaining a developer having good charging property and low-temperature fusing property which can be formed into finer particles.